Details

It seems the server is using a new authentication method unsupported by the version of ZEOSLib we are using (6.0.12). We cannot use 6.1.2 or higher (yet) because they are in beta stage.

Solution for the user is to reset the password of the MySQL user to use an old password style, as described in the MySQL documentation:

Reset the password to pre-4.1 style for each user that needs to use a pre-4.1 client program. This can be done using the SET PASSWORD statement and the OLD_PASSWORD() function:
mysql> SET PASSWORD FOR
-> 'some_user'@'some_host' = OLD_PASSWORD('newpwd');